Rotor including balancer weight and motor

ABSTRACT

A rotor capable of fixing a balancer weight by an easier method. The rotor includes a shaft; a core having a core hole penetrating the core in an axial direction; a rod configured to be inserted into the core hole so as to protrude from one end surface of the core in the axial direction to the one side in the axial direction; a balancer weight having a weight hole and placed on the end surface with the rod inserted into the weight hole; and a fixing member having a fixing hole and coming into contact with the balancer weight from the one side in the axial direction with the rod inserted into the fixing hole to fix the balancer weight by sandwiching the balancer weight with the end surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a rotor including a balancer weight foradjusting the rotational balance, and a motor.

2. Description of the Related Art

In a rotor of a motor, a technique of providing a balancer weight foradjusting rotational balance during operation is known (for example,Japanese Laid-open Patent Publication No. H2-246748, Japanese Laid-openPatent Publication No. 2003-319624, Japanese Unexamined Utility ModelApplication Publication No. H2-118450, and Japanese Examined UtilityModel Application Publication No. H7-9583).

In order to smoothly automate manufacturing steps of a rotor, atechnique capable of fixing a balancer weight to the rotor by an easiermethod is required.

SUMMARY OF THE INVENTION

In one aspect of the invention, a rotor of a motor comprises a shaft; acore fixed on radially outside of the shaft, and including a core holeextending through the core in an axial direction; and a rod insertedinto the core hole so as to protrude from an end surface of the core atone side in the axial direction toward the one side in the axialdirection.

In addition, the rotor comprises a balancer weight including a weighthole into which the rod is inserted, and placed on the end surface whilethe rod is inserted into the weight hole; and a fixing member includinga fixing hole into which the rod is inserted, and contacting thebalancer weight from the one side in the axial direction while the rodis inserted into the fixing hole, whereby holding the balancer weightbetween the fixing member and the end surface so as to fix the balancerweight.

The balancer weight and the fixing member may be annular. The fixingmember may include a spring part arranged around the fixing hole anddefining the fixing hole. The spring part may be elastically deformed toexpand by the rod when the rod is inserted into the fixing hole, andtighten the rod by the action of an elastic restoring force generated inthe spring part.

A slit, which extends from an inner edge of the spring part whichdefines the fixing hole toward an outer edge of the fixing member, maybe formed at the spring part. In another aspect of the invention, amotor comprises the above-described rotor.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-described and other objects, features, and advantages of theinvention will be clarified by describing the following preferredembodiment with reference to the attached drawings, in which:

FIG. 1 is a side view of a motor according to an embodiment of theinvention;

FIG. 2 is a side view of the rotor shown in FIG. 1;

FIG. 3 is a cross-sectional view of the rotor shown in FIG. 2 cut alongIII-III in FIG. 2;

FIG. 4 is a perspective view of the rotor shown in FIG. 2 seen from theaxially front side;

FIG. 5 is a front view of the balancer weight shown in FIG. 4;

FIG. 6 is a front view of the fixing member shown in FIG. 4; and

FIG. 7 is a cross-sectional view of the fixing member shown in FIG. 6cut along VII-VII in FIG. 6.

DETAILED DESCRIPTION

Hereinafter, an embodiment of the invention will be described in detailbased on the drawings. First, referring to FIG. 1, a motor 10 accordingto an embodiment of the invention will be described. Note that, in thefollowing description, an axial direction indicates a direction along arotation axis O₁ of a shaft 32 shown in FIG. 1, a radial directionindicates a radial direction of a circle centered about the axis O₁, anda circumferential direction indicates a circumferential direction of thecircle centered about the axis O₁. In addition, the frontward in theaxial direction (axially frontward) corresponds to the leftward in FIG.1.

The motor 10 includes a housing 14 defining an inner space 12; a stator16 fixed in the inner space 12 of the housing 14; and a rotor 30rotatably arranged at radially inside of the stator 16. The stator 16includes a stator core 18 and a coil 20 wound around the stator core 18.

Next, referring to FIG. 2 and FIG. 3, the rotor 30 according to thepresent embodiment will be described. The rotor 30 includes the shaft 32extending in the axial direction; a rotor core 34 fixed on the radiallyoutside of the shaft 32; and a plurality of magnets 36 arranged in therotor core 34.

The rotor 30 according to the present embodiment is a so-calledradial-type rotor. The rotor core 34 includes a plurality of coresegments 38 arranged to align in the circumferential direction at equalintervals; and a plurality of core segments 40 arranged at axially rearside of the core segments 38 so as to align in the circumferentialdirection at equal intervals.

Each of the core segments 38 and 40 is configured by a plurality ofmagnetic steel sheets (not shown in the drawings) stacked in the axialdirection. In the present embodiment, a total of eight core segments 38and a total of eight core segments 40 are placed.

Each of the core segments 38 includes a hole 46 extending through thecore segment 38 in the axial direction. Similarly, each of the coresegments 40 includes a hole 48 extending through the core segment 40 inthe axial direction.

The core segment 38 and the core segment 40 are positioned relative toeach other so that the hole 46 and the hole 48 straightly align in theaxial direction. One magnet 36 is arranged between two core segments 38adjoining each other in the circumferential direction. Similarly, onemagnet 36 is arranged between two core segments 40 adjoining each otherin the circumferential direction. Therefore, in the present embodiment,a total of sixteen magnets 36 are arranged.

Each of the magnets 36 has a square pole shape having a predeterminedlength, height, and width. Each of the magnets 36 is positioned relativeto the core segments 38 and 40 so that the length direction thereof isalong the axial direction, the height direction thereof is along theradial direction, and the width direction thereof is along thecircumferential direction.

The rotor core 34 further includes two end plates 42 and 44. The endplate 42 is arranged on an end surface 38 a of the core segment 38 atthe axially front side. On the other hand, the end plate 44 is arrangedon an end surface 40 a of the core segment 40 at the axially rear side.

The end plate 42 includes a total of eight holes 50 formed at positionscorresponding to the holes 46 of the core segments 38. On the otherhand, the end plate 44 includes a total of eight holes 52 formed atpositions corresponding to the holes 48 of the core segments 40.

Thus, the hole 50 of the end plate 42, the hole 46 of the core segment38, the hole 48 of the core segment 40, and the hole 52 of the end plate44 align in the axial direction so as to constitute a core hole 54 whichextending through the rotor core 34 in the axial direction. In this way,a total of eight core holes 54 arranged to align in the circumferentialdirection at equal intervals are formed in the rotor core 34.

A rod 56 extending in the axial direction is inserted into each of thecore holes 54. In the present embodiment, as shown in FIG. 3, a total ofeight substantially cylindrical rods 56 are arranged. Each of the rods56 is arranged so as to protrude from an axially front end surface 42 aof the end plate 42 to axially frontward and to protrude from an axiallyrear end surface 44 a of the end plate 44 to axially rearward.

Here, the rotor 30 according to the present embodiment further includesat least one balancer weight 60 and at least one fixing member 62 forfixing the balancer weight 60. Next, referring to FIG. 4 to FIG. 7, thebalancer weight 60 and the fixing member 62 according to the presentembodiment will be described.

In FIG. 4, the balancer weight 60 and the fixing member 62 are attachedto one rod 56, while only the fixing members 62 are attached to theother two rods 56. As shown in FIG. 5, the balancer weight 60 is anannular member having a weight hole 60 a. The balancer weight 60 is amember for adjusting the rotational balance of the rotor 30 when therotor 30 rotates, and has a predetermined weight.

As shown in FIG. 6 and FIG. 7, the fixing member 62 is an annular memberhaving a fixing hole 64. More specifically, the fixing member 62includes an annular flat plate part 66; a cylindrical outer plate part68 extending from the outer peripheral edge of the flat plate part 66 toaxially frontward; and a truncated cone-shaped spring plate part 70extending from the inner peripheral edge of the flat plate part 66 toaxially frontward so as to be slanted relative to the flat plate part66.

The fixing hole 64 of the fixing member 62 is surrounded by the springplate part 70, and defined by the inner edge of the spring plate part70. A plurality of slits 72 are formed at the spring plate part 70. Eachof the slits 72 is formed at the spring plate part 70 so as to extendfrom the inner edge of the spring plate part 70 (i.e., the fixing hole64) toward the outer plate part 68 along a virtual line L radiallyextending from a central axis O₂ of the fixing member 62.

Referring to FIG. 4 again, the balancer weight 60 is arranged so as tocontact the end surface 42 a of the end plate 42 while the rod 56 isinserted into the weight hole 60 a. On the other hand, the fixing member62 is arranged so as to contact the balancer weight 60 from axiallyfront side while the rod 56 is inserted into the fixing hole 64.

Here, the inner diameter of the fixing hole 64 of the fixing member 62is set to be smaller than the outer diameter of the rod 56. Therefore,the spring plate part 70 is elastically deformed to expand by the rod 56when the rod 56 is inserted into the fixing hole 64 of the fixing member62, whereby the diameter of the inner edge of the spring plate part 70,i.e., the fixing hole 64, is enlarged.

Then, the rod 56 is tightened by the inner edge of the spring plate part70 by the action of the elastic restoring force generated in the springplate part 70. Due to this, the movement of the fixing member 62relative to the rod 56 is prevented, whereby the fixing member 62 isfixed to the rod 56 by so-called interference fit.

The balancer weight 60 is held between the end surface 42 a of the endplate 42 and the fixing member 62 so as to be fixed therebetween. If thebalancer weight 60 is not placed and only the fixing member 62 is placedon the rod 56, the fixing member 62 is arranged to contact the endsurface 42 a of the end plate 42.

The number and the weight of the balancer weights 60 are appropriatelyset depending on parameters such as the maximum rotation frequency ofthe motor 10, etc. In addition, in the present embodiment, the fixingmember 62 functions as a second balancer weight for adjusting therotational balance of the rotor 30 together with the balancer weight 60.Therefore, the number and the weight of the fixing members 62 areappropriately set, depending on parameters such as the maximum rotationfrequency of the motor 10, and on the number and the weight of thebalancer weights 60.

Thus, according to the present embodiment, it is possible to easilyattach the balancer weight 60 by sandwiching the balancer weight 60between the fixing member 62 and the end surface 42 a of the end plate42. As a result, an attaching operation of the balancer weight 60 can beadvantageously automated, so it is possible to improve the manufacturingefficiency. In addition, it is possible to reduce the number ofcomponents since any additional structure for attaching the balancerweight 60 is not required.

Note that, in the above-described embodiment, a case is described wherethe balancer weight 60 is arranged on the end surface 42 a of the endplate 42. However, the balancer weight 60 may be arranged on the endsurface 44 a of the end plate 44. In this case, the fixing member 62 isarranged to contact the balancer weight 60 from axially rear side,whereby hold the balancer weight 60 between the fixing member 62 and theend surface 44 a of the end plate 44 to fix the balancer weight 60.

Further, in the above-described embodiment, a case is described wherethe rod 56 has a cylindrical shape. However, the rod 56 may have amultangular shape, for example. In this case, the core hole 54 (i.e.,the hole 50 of the end plate 42, the hole 46 of the core segment 38, thehole 48 of the core segment 40, and the hole 52 of the end plate 44) isformed to have a shape corresponding to the outer shape of the rod 56.Further, a fixing hole of a fixing member is formed to have an innersize smaller than that of the outer periphery of the rod.

In addition, in the above-described embodiment, a case is describedwhere the rotor 30 is a so-called radial type. However, the rotor 30 maybe any type of rotors. For example, a rotor may include an annular rotorcore continuously extending in the circumferential direction, and aplurality of arc-shaped magnets arranged in the rotor core so as toalign in the circumferential direction.

Heretofore, the invention has been described by way of the embodiment ofthe invention, but the above-described embodiment does not limit theinvention according to claims. In addition, forms obtained by combiningthe features described in the embodiment of the invention can beincluded in the technical scope of the invention, but all of thesecombinations of the features are not necessarily essential for thesolving means of the invention. Furthermore, it is obvious for a personskilled in the art that various modifications or improvements can beadded to the above-described embodiment.

The invention claimed is:
 1. A rotor of a motor comprising: a shaft; acore fixed on radially outside of the shaft, and including a pluralityof core holes extending through the core in an axial direction; aplurality of rods respectively inserted into the core holes so as toprotrude from an end surface of the core at one side in the axialdirection toward the one side in the axial direction; a balancer weightincluding a weight hole into which a first rod of the plurality of rodsis inserted, and placed on the end surface while the first rod isinserted into the weight hole; a first fixing member including a firstfixing hole into which the first rod is inserted, and contacting thebalancer weight from the one side in the axial direction while the firstrod is inserted into the first fixing hole, whereby holding the balancerweight between the first fixing member and the end surface so as to fixthe balancer weight, wherein an inner edge of the first fixing memberwhich defines the first fixing hole tightens the first rod so that themovement of the first fixing member relative to the first rod isprevented when the first rod is inserted into the first fixing hole; anda second fixing member including a second fixing hole into which asecond rod of the plurality of rods is inserted, and contacting the endsurface from the one side in the axial direction while the second rod isinserted into the second fixing hole, wherein an inner edge of thesecond fixing member which defines the second fixing hole tightens thesecond rod so that the movement of the second fixing member relative tothe second rod is prevented when the second rod is inserted into thesecond fixing hole.
 2. The rotor according to claim 1, wherein thebalancer weight, the first fixing member, and the second fixing memberare annular.
 3. The rotor according to claim 1, wherein each of thefirst and second fixing members includes a spring part arranged aroundthe fixing hole and defining the fixing hole, wherein the spring part ofthe first fixing member is elastically deformed to expand by the firstrod when the first rod is inserted into the first fixing hole, andtightens the first rod by the action of an elastic restoring forcegenerated in the spring part of the first fixing member, and wherein thespring part of the second fixing member is elastically deformed toexpand by the second rod when the second rod is inserted into the secondfixing hole, and tightens the second rod by the action of an elasticrestoring force generated in the spring part of the second fixingmember.
 4. The rotor according to claim 3, wherein the spring part ofthe first fixing member is formed with a slit extending from the inneredge of the spring part of the first fixing member, which defines thefirst fixing hole, toward an outer edge of the first fixing member, andwherein the spring part of the second fixing member is formed with aslit extending from the inner edge of the spring part of the secondfixing member, which defines the second fixing hole, toward an outeredge of the second fixing member.
 5. A motor comprising the rotoraccording to claim 1.